The deployment of 21,500 additional U.S. troops in Iraq probably will last at least until the end of the summer, a top general said yesterday, urging patience with President Bush's strategy while a bipartisan group of U.S. legislators continued pressing for a new plan.

Gen. George W. Casey Jr., the top U.S. military officer in Iraq, said that the primary focus of the additional U.S. forces will be to secure a violent Baghdad and that their mission, if it goes as planned, could last well into 2007. He and other defense officials have said in recent days that the new battle for Baghdad could take some time but that it will be apparent in coming months whether progress is being made.

"That's not going to happen overnight either, and you're going to see some progress gradually over the next 60 to 90 days," Casey told reporters in southern Iraq yesterday, according to a transcript. "But I think it's probably going to be the summer, late summer, before we get to the point where the people in Baghdad feel safe in their neighborhoods. . . . The first troops are just arriving now, so we've got to wait and see the effect they have on the situation here before we even start thinking about when we might send them home."

The president's plan has drawn ire from Democrats who see the November elections as a mandate to change course in Iraq. House Speaker Nancy Pelosi (D-Calif.) lashed out in an ABC News interview aired yesterday, saying that Bush has "dug a hole so deep he can't even see the light on this" and calling the buildup "a stark blunder."

"The president knows that because the troops are in harm's way, that we won't cut off the resources," Pelosi told ABC. "That's why he's moving so quickly to put them in harm's way, but we will hold the president accountable. He has to answer for his war."

"I think questioning the president's motivations and suggesting that he, for some political reason, is rushing troops into harm's way, is not appropriate, it is not correct, and it is unfortunate because we do have troops in harm's way," Perino said at a news conference.

In a speech at the National Press Club yesterday with Senate Majority Leader Harry M. Reid (D-Nev.), Pelosi said the war has produced tens of thousands of casualties, cost hundreds of billions of dollars and damaged the country's standing internationally. She said it also has strained the U.S. military and thus threatens national security.

"Escalating our military involvement in Iraq will not reverse these negative effects. It will only add to them," Pelosi said.

Reid echoed Pelosi's position: "Unfortunately, the president's new plan can be summed up in four words: 'more of the same.' Like our military generals, the American people, and a growing bipartisan chorus in Congress, I believe escalation is a serious mistake . . . Interjecting more U.S. military forces will not end this civil war."

Yesterday, a bipartisan group from the Senate Armed Services Committee announced it will give a resolution on Monday "addressing the president's plan to augment U.S. military forces in Iraq."

The chief sponsor of the resolution, Sen. John W. Warner (Va.), the ranking Republican of the committee, has expressed reservations about putting U.S. forces in the middle of a sectarian fight in Baghdad and has openly questioned sending more troops. Warner's public comments suggest his plan will fall somewhere between the president's strategy and the Democrats' position.

Casey explained his request for more troops yesterday, indicating that he saw three reasons for a more robust presence: the deteriorating situation in Baghdad; the commitments from the Iraqi government that will allow free U.S. troop movement throughout the city; and the fact that Iraqi forces have not been reliable enough "where we could count on them to do the right thing without additional coalition support."

The increased demand for U.S. troops in Iraq is likely to lead to an early, involuntary call-up late this year or early next year of about four Army National Guard combat brigades with 3,500 to 4,000 troops each, Pentagon officials said.

The Army had planned to be able to supply 18 or 19 combat brigades for Iraq and other overseas duty continually, but the requirement is now for 23, placing a heavy burden on the active-duty Army, said Lt. Gen. Stephen M. Speakes, Army deputy chief of staff, in a Pentagon briefing yesterday. The mobilization of guard brigades will allow active-duty combat units to spend more time at home.

To further ease the strain, the Army and Marine Corps are starting a push to expand their ranks by 12,000 additional troops each year for the next five years, leading senior Pentagon officials to appeal for greater public support for military service. The increase will require a combination of retaining troops and recruiting.